If you're looking to go full on with this, taking your amp to Rev C specs, here are the changes you would have to make,
I'd call it more of a "reversion" to old specs than a "mod"
Remove R277 and install a jumper.
Remove R272 and install a jumper, change the cap at C55 from .10uf to .0047uf. (the smaller orange drop cap in front of the larger 3)
Remove R271 and install a jumper.
Remove R110 (680k) and replace with a 470k, remove R322 and C10 (both which are behind that red cap.
Clip and jump LDR 4, just cut the leads as close as you can to the body of the LDR and just solder the leads together on both sides.
You can also just solder a jump across the resistors/caps that I've removed if you want to make this reversible.
Another thing you can do to add a little more brightness/cut is to lift C12, opens up the high end a bit.
I left this cap in since it helps define the recto voice a bit.
This includes changing both gain pots to 1 meg, changing the presence pot to 250k in the Red channel. I left the 25k in the orange channel since the whole amp gets brightened up with the single pot change to 25ok in the red channel.
Doing this will boost your high gain tones significantly, but will however cause your cleans to have grit to them (but if you slowly raise the gain you'll find a nice sweet spot) It will also clear up that fizz.
I however rarely use cleans so this was right up my alley.
However, use caution while desoldering/soldering in these tight areas, these traces can lift if you use too much heat with your iron.
If you don't have an adjustable soldering station use a 15-25w iron, or keep your soldering station at 650-700F.
